During the production and gathering of crude oil in the oilfield, the crude produced from the borehole contains various undesirable substances, including water, sour gas, and foreign debris. It is therefore desirable to treat the crude before it is placed in the oil pipeline. A heater treater is usually employed for separating the crude from these other undesirable substances, and the treated oil is called "pipeline oil" because of its cleanliness. The heater treater causes the water and debris to gravitate in a downward direction and the sour gas to rise in an upward direction so that the pipeline oil emerges from the heater treater. A fire tube combustion type heat exchanger heats the contaminated incoming crude oil to a predetermined and closely controlled maximum temperature so as to prevent the paraffins from separating therefrom. Heater treaters are available from a number of different commercial manufacturers.
Until recently, there was usually an abundance of natural gas available for the fire tube of the heater treater, and no one was particularly concerned over the efficiency of combustion of the fire tube burner. As a matter of fact, when most of the present day heater treaters were designed and installed in the oilfield, natural gas was a waste product, and it was common to see the entire oilpatch lit up at night from the "flares" which wasted the excess natural gas into the atmosphere.
The crude leaving the heater treater must be pumped to a storage tank; and therefore, especially in the winter time, it is desirable that the oil have a low viscosity to facilitate flow through the pipeline.
It is common to utilize the treated hot oil to heat the incoming untreated crude. This represents an advantage during the warm summer months, but is often a detriment during the winter months, especially where the treated crude must be pumped a long distance.
It would therefore be desirable to increase the efficiency of a heater treater by utilizing the wasted flue gases from the combustion burner of the fire tube, thereby enabling the oil-to-oil heat exchanger to be eliminated, and also enabling greater thermal efficiency of the entire heater treater system to be achieved. Such a desirable expedient is the subject of this invention.